1. Field of the Invention
The invention relates to the construction of an underground reservoir or a cave depot, and more particularly to a method and device for construction of an underground reservoir or a cave depot in limestone geology.
2. Description of the Related Art
Underground energy/waste reservoir can be used for storage of natural gas, oil, and other energy resources, thereby being an indispensable part for a large gas transmission trunk line system. Nuclear waste or carbon dioxide can also be preserved in the underground energy/waste reservoir, which is conducive to national security, energy supply, and environmental improvement. Conventionally, large-scale underground energy/waste reservoirs are generally constructed in mined oil and gas reservoirs, abandoned mines, underground saline aquifers and underground rock salt deposits. Limited by specific geological conditions, the oil and gas pipeline networks and the oil and gas consumption centers are not necessarily located in a geological environment suitable for constructing reservoirs, thereby greatly affecting the development of the underground repository. Thus, it is urgent to develop a universal method for construction of underground reservoirs in various geological zones. Limestone has a wide distribution in the stratum layer, low permeability, and good sealing performance. In the process of diagenesis, limestone is hardly affected by karstification, and thus the natural fissures thereof do not expand, and are even filled with calcite and clay. Therefore, the underground limestone layer has the basic geological conditions for constructing underground energy and waste reservoirs.
U.S. Pat. No. 7,156,579B2 discloses a method for constructing a gas reservoir in limestone layers. The method employs hydrochloric acid to dissolve limestone to construct the gas reservoir. The chemical equation for dissolving limestone is as follows:CaCO3+2HCl→CaCl2+CO2+H2O
As shown from the chemical equation, a large amount of carbon dioxide is produced in the process of cavern making, which is apt to cause greenhouse effect and environmental pollution if not being dealt properly.